The study, Online counseling to enable lifestyle-focused obesity treatment in primary care, aims to translate an evidence-based lifestyle intervention into the primary care setting, using information technology to enable clinical lifestyle counseling. While the US Preventive Services Task Force (USPSTF) recommends that clinicians screen all adult patients for obesity and offer intensive counseling and behavioral interventions to promote sustained weight loss for obese adults, multiple barriers to intensive lifestyle counseling exist and the recommendation has not been widely implemented. We propose to examine two coaching strategies for delivering an online version of a comprehensive intervention combining diet and exercise advice with behavioral tools. This intervention, originally developed for the Diabetes Prevention Program (DPP), is consistent with the counseling approach recommended by the USPSTF and has proven efficacy for promoting weight loss. We will randomize patients to one of three study arms, comparing the effect of the two online coaching strategies for delivering the Internet-based DPP intervention with a third arm in which patients are provided specific lifestyle goals and online links to community resources that support lifestyle change. By requiring physician referral, augmenting the health care team's access to behavioral expertise, and encouraging physician feedback to participating patients, we aim to integrate lifestyle issues into routine preventive medicine. In the arms based on the DPP intervention, an Internet-based approach allows us to combine intensive evidence-based counseling with relatively low staffing needs and extraordinary flexibility in terms of patients scheduling and location preferences. We will examine change in weight, waist circumference, physical activity, quality of life, and will calculate intervention cost- effectiveness. We will ensure sustainability by using recruitment and adherence strategies that can be replicated in routine practice, and counseling staff who are representative of the educators employed in primary care practice. If an online strategy is effective, the extensive network of the University of Pittsburgh Medical Center Health System provides excellent infrastructure for supporting dissemination in the region. As such, this study may facilitate wide-spread adoption of current evidence-based preventive medicine guidelines recommending incorporation of intensive lifestyle interventions into primary care practice.